PORTLAND, Ore. (AP) – Courts and legislatures are slowly shifting away from using eyewitness testimony as the gold standard of evidence. The reason: Studies show it’s only right about half the time.

That has led a small group of police chiefs, courts and lawmakers to toughen laws governing the handling of eyewitnesses and their accounts of crimes. Reform advocates say procedures long regarded as solid police work can fundamentally alter what someone believes they saw.

Prosecutors have pushed back against the effort politically. National District Attorneys Association director Scott Burns says reform efforts are targeted at undercutting prosecutors.

State supreme courts in Oregon and New Jersey implemented stringent guidelines for eyewitness testimony. Legislatures in seven states, from Connecticut to North Carolina, along with a number of cities have overhauled their treatment of eyewitness testimony.